I am a new user to Pov-ray.
I have experience writing C code but not C++.
my question is this:
I am atempting to create an image from photometric lightcurve data of an
asteroid.
Does anybody know of code available for lightcurve inversion or will i have
to try and write some myself??

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"Dan_The_Man" <dan### [at] hotmailcom> wrote in message 
news:web.43c4245891cc8ba33a6d2d290@news.povray.org...
> I have experience writing C code but not C++.
> I am atempting to create an image from photometric lightcurve data of an
> asteroid.
> Does anybody know of code available for lightcurve inversion

I don't. Could be interesting stuff.

Is it based on rotation and time, then?

Making guesses here, but it might only cover one brightness change during a 
one-axis spin, or something like that. Basically similar to a variable star 
lightcurve, perhaps, so the shape and brightness would be seen as the same 
thing. In fact, if it were more complex data than that, you might have a lot 
of work ahead by having to figure other aspects, such as precession, if it 
is indeed only a lightcurve varying over multiple spins of the asteroid. 
Still, sounds intriguing to try and create a surface texture or shape from 
such information.

In the most simplistic way I think it should be easy to just vary color 
(brightness) across the face of a sphere. Nothing much to that. If there are 
multiple spins then a series of spheres (blob) could be textured separately 
along a spline, so that it creates both a surface and brightness as it goes 
around a central point. That would probably be what I'd try anyway. Not sure 
of meshes or other possibilities but other people could say if they see your 
message and reply. A lot depends on the actual way that data is done.

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thanks for your reply
yes indeed it is very like a variable star lightcurve. although here the
change in brightness is cause almost entirely from the shape of the
asteroid, albedo effects are not as important as the shape.
all i need is an algorithm to convert the change in intensity relative to
the phase (over a single period i mite add) to that of the shape of a
convex hull.
any ideas??

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"Dan_The_Man" <dan### [at] hotmailcom> wrote in message 
news:web.43c66fc0e7dfbc3a6d2d290@news.povray.org...
> thanks for your reply

Welcome to it, few and far between as they are.

> yes indeed it is very like a variable star lightcurve. although here the
> change in brightness is cause almost entirely from the shape of the
> asteroid, albedo effects are not as important as the shape.
> all i need is an algorithm to convert the change in intensity relative to
> the phase (over a single period i mite add) to that of the shape of a
> convex hull.
> any ideas??

Thinking this over again...

The two ideas I had in mind before are imperfect for what you're asking... 
from what I can figure anyway.

The first, a variable brightness change across the face of a sphere, 
wouldn't show any shape. I understand you're saying that the asteroid would 
instead most likely need to be modeled with size changes based on the 
orientation the lightcurve is meant to deduce-- or show faces oriented 
toward the observation in a relative size according to brightness.

The second, using an object with size change as it wraps around a central 
point, would cause the smaller sides to be overwhelmed by the larger sides 
unless the distance they are placed outward from the central point happened 
to be farther than the distance the largest sides are in breadth and height. 
In other words, overlap could negate the smallest dimensions or the 
distended shape could look like a chewed donut if seen from above. Hopefully 
I'm describing this in a way that makes sense to you.

Although I'm fresh out of really good ideas at the moment at least I have 
one other suggestion. You might get some more responses by asking at the 
povray.general group since here at povray.newusers the questions and answers 
are usually about basic things concerning POV-Ray itself (not sure how many 
people visit here). Sorry that this didn't occur to me before now, might 
have delayed potential solutions.

I' probably overlooking a simple answer anyway. Also, something I hadn't 
mention before is about the method to get the data into POV. You should be 
able to set up a #read from a file containing the lightcurve values so that 
it is used by an object (or texture, or...?) to create the asteroid model. 
But since my ideas are probably flawed I didn't bother to show an example 
here. Anyhow, you could be checking into file #open or #read found in the 
Help so you can get a grasp of the subject if you don't already know of 
that.

Bob

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